In "Settings->Window Manager" I can customize keyboard shortcuts for actions such as window tiling or maximizing and minimizing windows. There is no option to control the volume with keyboard, though. It is possible in Cinnamon which has a similar control panel for keys but I don't know how to do it in Xfce.

I ended up choosing this way because it's easier to work with if you want to change the volume of a device other than Master. I set the default audio device using pacmd set-default-sink $index and can use the same index to adjust volume.
– Martin AnderssonSep 22 '18 at 17:52